Organic fuel cell methods and apparatus

ABSTRACT

A liquid organic, fuel cell is provided which employs a solid electrolyte membrane. An organic fuel, such as a methanol/water mixture, is circulated past an anode of a cell while oxygen or air is circulated past a cathode of the cell. The cell solid electrolyte membrane is preferably fabricated from Nafion™. Additionally, a method for improving the performance of carbon electrode structures for use in organic fuel cells is provided wherein a high surface-area carbon particle/Teflon™-binder structure is immersed within a Nafion™/methanol bath to impregnate the electrode with Nafion™. A method for fabricating an anode for use in a organic fuel cell is described wherein metal alloys are deposited onto the electrode in an electro-deposition solution containing perfluorooctanesulfonic acid. A fuel additive containing perfluorooctanesulfonic acid for use with fuel cells employing a sulfuric acid electrolyte is also disclosed. New organic fuels, namely, trimethoxymethane, dimethoxymethane, and trioxane are also described for use with either conventional or improved fuel cells.

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application is a divisional application of U.S. applicationSer. No. 08/478,801, filed Jun. 7, 1995, which is a continuationapplication of U.S. application Ser. No. 08/135,007, filed Oct. 12,1993.

BACKGROUND OF THE INVENTION

[0002] 1. Origin of the Invention

[0003] The invention described herein was made in the performance ofwork under a NASA contract, and is subject to the provisions of PublicLAW 96-517 (35 USC 202) in which the Contractor has elected to retaintitle.

[0004] 2. Technical Field

[0005] The invention generally relates to organic fuel cells and inparticular liquid feed organic fuel cells.

[0006] 3. Background Art

[0007] Fuel cells are electrochemical cells in which a free energychange resulting from a fuel oxidation reaction is converted intoelectrical energy. In an organic/air fuel cell, an organic fuel such asmethanol, formaldehyde, or formic acid is oxidized to carbon dioxide atan anode, while air or oxygen is reduced to water at a cathode. Fuelcells employing organic fuels are extremely attractive for bothstationary and portable applications, in part, because of the highspecific energy of the organic fuels, e.g., the specific energy ofmethanol is 6232 Wh/kg.

[0008] Two types of organic/air fuel cells are generally known:

[0009] 1. An “indirect” or “reformer” fuel cell in which the organicfuel is catalytically reformed and processed into carbon monoxide-freehydrogen, with the hydrogen so obtained oxidized at the anode of thefuel cell.

[0010] 2. A “direct oxidation” fuel cell in which the organic fuel isdirectly fed into the fuel cell without any previous chemicalmodification where the fuel is oxidized at the anode.

[0011] Direct oxidation fuel cells do not require a fuel processingstage. Hence, direct oxidation fuel cells offer a considerable weightand volume advantage over the indirect fuel cells. Direct oxidation fuelcells use either a vapor or a liquid feed of the organic fuel. Currentart direct oxidation fuel cells that have shown promise typically employa liquid feed design in which a liquid mixture of the organic fuel and asulfuric acid electrolyte is circulated past the anode of the fuel cell.

[0012] The use of sulfuric acid electrolyte in the current-art directmethanol fuel cells presents several problems. The use of sulfuric acid,which is highly corrosive, places significant constraints on thematerials of construction of the fuel cell. Typically, expensivecorrosion resistant materials are required. Sulfate anions, createdwithin the fuel cell, have a strong tendency to adsorb on theelectrocatalyst, thereby hindering the kinetics of electro-oxidation ofthe fuel and resulting in poor performance of the fuel electrode. Also,sulfuric acid tends to degrade at temperatures greater than 80° C. andthe products of degradation usually contain sulfur which can poison theelectrocatalyst. In multi-cell stacks, the use of sulfuric acidelectrolyte can result in parasitic shunt currents.

[0013] Exemplary fuel cells of both the direct and indirect types aredescribed in U.S. Pat. Nos.: 3,013,908; 3,113,049; 4,262,063; 4,407,905;4,390,603; 4,612,261; 4,478,917; 4,537,840; 4,562,123; and 4,629,664.

[0014] U.S. Pat. Nos. 3,013,908 and 3,113,049, for example, describeliquid feed direct methanol fuel cells using a sulfuric acidelectrolyte. U.S. Pat. Nos. 4,262,063, 4,390,603, 4,478,917 and4,629,664 describe improvements to sulfuric acid-based methanol fuelcells wherein a high molecular weight electrolyte or a solid protonconducting membrane is interposed between the cathode and the anode asan ionically conducting layer to reduce crossover of the organic fuelfrom the anode to the cathode. Although the use of the ionicallyconducting layer helps reduce crossover, the tonically conducting layeris used only in conjunction with a sulfuric acid electrolyte. Hence, thefuel cell suffers from the various aforementioned disadvantages of usingsulfuric acid as an electrolyte.

[0015] In view of the aforementioned problems associated with usingsulfuric acid as an electrolyte, it would be desirable to provide aliquid feed fuel cell that does not require sulfuric acid as anelectrolyte.

[0016] In addition to the improvements in operational characteristics ofthe liquid feed fuel cell, the conventional method of fabricatinghigh-surface-area electro-catalytic electrodes for use such fuel cellsalso needs to be improved. The existing method of fabrication of fuelcell electrodes is a fairly time-consuming and expensive procedure.Specifically, electrode fabrication requires that a high surface-areacarbon-supported alloy powder be initially prepared by a chemical methodwhich usually requires about 24 hours. Once prepared, the carbonsupported alloy powder is combined with a Teflon™ binder and applied toa carbon fiber-based support to yield a gas diffusion electrode. Tovolatilize impurities arising out of the Teflon™ binder and to obtain afibrous matrix of Teflon™, the electrodes are heated to 200-300° C.During this heating step, oxidation and sintering of the electrocatalystcan occur, resulting in a reduced activity of the surface of theelectrode. Thus, the electrodes often require re-activation before use.

[0017] Also electrodes produced by conventional methods are usually ofthe gas-diffusion type and cannot be effectively used in liquid feedtype fuel cells as the electrode is not adequately wetted by the liquidfuel. In general, the structure and properties of a fuel oxidationelectrode (anode) for use in liquid feed type fuel cells are quitedifferent from the gas/vapor feed fuel cells such as the hydrogen/oxygenfuel cell. The electrode structures for use in a liquid feed fuel cellshould be very porous and the liquid fuel solution should wet all pores.Carbon dioxide that is evolved at the fuel electrode should beeffectively released from the zone of reaction. Adequate wetting of theelectrodes is a major problem for liquid feed fuel cells—even for thosewhich use a sulfuric acid electrolyte.

[0018] As can be appreciated, it would be desirable to provide improvedmethods for fabricating electrodes, particularly for use in liquid feedfuel cells. It is also desirable to devise methods for modifyingelectrodes, originally adapted for gas-feed fuel cells, for use inliquid feed fuel cells.

[0019] In addition to improving the liquid feed fuel cell itself and forproviding improved methods for fabricating the electrodes of fuel cell,it would be desirable to provide new effective fuels as well. Ingeneral, it is desirable to provide liquid fuels which undergo clean andefficient electro-chemical oxidation within the fuel cell. The efficientutilization of organic fuels in direct oxidation fuel cells is, ingeneral, governed by the ease by which the organic compounds areanodically oxidized within the fuel cell. Conventional organic fuels,such as methanol, present considerable difficulties with respect toelectro-oxidation. In particular, the electro-oxidation of organiccompounds such as methanol involves multiple electron transfer and is avery hindered process with several intermediate steps. These stepsinvolve dissociative adsorption of the fuel molecule to form activesurface species which undergo relatively facile oxidation. The ease ofdissociative adsorption and surface reaction usually determines thefacility of electro-oxidation. Other conventional fuels, such asformaldehyde, are more easily oxidized, but have other disadvantages aswell. For example, formaldehyde is highly toxic. Also, formaldehyde isextremely soluble in water and therefore crosses over to the cathode ofthe fuel cell, thus reducing the performance of the fuel cell. Otherconventional organic fuels, such as formic acid, are corrosive.Furthermore, many of the conventional organic fuels poison theelectrodes of the fuel cell during electro-oxidation, thus preventingsustained operation. As can be appreciated, it would be desirable toprovide improved fuels, particularly for use in liquid feed fuel cells,which overcome the disadvantages of conventional organic fuels, such asmethanol, formaldehyde, and formic acid.

SUMMARY OF THE INVENTION

[0020] A general object of the invention is to provide an improveddirect type liquid feed fuel cell. One particular object of theinvention is to provide a direct type liquid feed fuel cell which doesnot require a sulfuric acid electrolyte. Another particular object ofthe invention is to achieve adequate wetting of electrodes for use inliquid feed fuel cells. Yet another particular object of the inventionis to provide an improved method for wetting electrodes for use in fuelcells having sulfuric acid electrolytes. Still another particular objectof the invention is to provide improved fuels for use in liquid feedfuel cells.

[0021] The object of providing an improved liquid feed direct fuel cellwhich does not require a sulfuric acid electrolyte is achieved in partby using a solid polymer electrolyte membrane in combination with abattery-type anode that is porous and is capable of wetting the fuel. Inthe improved liquid feed fuel cell, a battery-type anode structure and acathode are bonded to either side of the solid polymer proton-conductingmembrane forming a membrane-electrode assembly. A solution of methanoland water which is substantially free of sulfuric acid is circulatedpast the anode side of the assembly.

[0022] A solid polymer membrane is used, in part, because such membraneshave excellent electrochemical and mechanical stability, high ionicconductivity, and can function both as an electrolyte and as aseparator. Also, the kinetics of electro-oxidation of methanol andelectro-reduction of air or oxygen are more facile at anelectrode/membrane-electrolyte interface as compared to anelectrode/sulfuric acid interface. The use of the membrane permitsoperation of the fuel cell at temperatures as high as 120° C. Since thefuel and water solution is substantially free of sulfuric acid, there isno need for expensive corrosion-resistant components in the fuel celland its accessories. Also the absence of conducting ions in the fuel andwater solutions, which can exist when a sulfuric acid electrolyte isemployed, substantially eliminates the possibility of any parasiticshunt currents in a multi-cell stack.

[0023] The solid polymer electrolyte is preferably a proton-conductingcation-exchange membrane, such as the perflourinated sulfonic acidpolymer membrane, Nafion™. Nafion™ is a copolymer of tetrafluoroethyleneand perfluorovinylether sulfonic acid. Membranes of modifiedperflourinated sulfonic acid polymer, polyhydrocarbon sulfonic acid andcomposites of two or more kinds of proton exchange membranes can also beused.

[0024] The anode is preferably formed from high surface area particlesof platinum-based alloys of noble and non-noble metals. Binary andternary compositions can be used for the electro-oxidation of organicfuels. Platinum-ruthenium alloy, with compositions varying from 10-90atom percent of platinum, is the preferred anode electrocatalyst for theelectro-oxidation of methanol. The alloy particles are either in theform of fine metal powders, i.e., “unsupported”, or are supported onhigh surface area carbon material.

[0025] Conventional fuel cell anode structures (gas diffusion type) arenot suitable for use in liquid feed type organic/air fuel cells. Theseconventional electrodes have poor fuel wetting properties. Theseconventional electrodes can be modified for use in liquid feed type fuelcells by coating them with substances that improve their wettingproperties. Nafion™ with an equivalent weight of 1000 or higher is thepreferred substance. The additive decreases interfacial tension of theliquid/catalyst interface and leads to the uniform wetting of theelectrode pores and particles by the fuel and water solution, yieldingenhanced utilization of the electrocatalyst. In addition to improvingwetting properties, Nafion™ additive also provides ionic continuity withthe solid electrolyte membrane and permits efficient transport ofprotons or hydronium ions generated by the fuel oxidation reaction.Further, the additive facilitates the release of carbon dioxide from thepores of the electrode. By using a perfluorinated sulfonic acid as theadditive, anionic groups are not strongly adsorbed on theelectrode/electrolyte interface. Consequently, the kinetics ofelectro-oxidation of methanol are more facile than in sulfuric acidelectrolyte. Other hydrophilic proton-conducting additives with thedesired properties include montmorrolinite clay, alkoxycelluloses,cyclodextrins, mixtures of zeolites, and zirconium hydrogen phosphate.

[0026] The object of improving electrodes for operating in liquid feedfuel cells is achieved, in part, by using perfluorooctanesulfonic acidas an additive in an electro-deposition bath used in fabricating theelectrode. An electro-deposition method using theperfluorooctanesulfonic acid additive comprises the steps of positioninga high-surface-area carbon electrode structure within a bath containingmetallic salts, positioning an anode within the bath and applying avoltage between the anode and the cathode until a desired amount ofmetal becomes deposited onto the electrode. After deposition of themetal onto the electrode, the electrode is extracted from the bath andwashed within deionized water.

[0027] Preferably, the metal salts include hydrogen hexachloroplatinateand potassium pentachloroaquoruthenium. The anode is composed ofplatinum. The carbon electrode structure includes high-surface-areacarbon particles bound together by polytetrafluoroethylene, sold underthe trademark Teflon™.

[0028] The object of providing for adequate wetting of an electrodewithin a liquid feed fuel cell having a sulfuric acid electrolyte isachieved by employing perfluorooctanesulfonic acid as an additive to thefuel mixture of the fuel cell. Preferably, the perfluorooctanesulfonicacid is added to the organic fuel and water mixture in concentrationsfrom 0.001-0.1 M.

[0029] The general objective of providing new fuels for use in organicfuel cells is achieved by using either trimethoxymethane,dimethoxymethane or trioxane. All three new fuels can be oxidized at ahigh rate into carbon dioxide and water within the fuel cell withoutpoisoning the electrodes. Furthermore, neither trimethoxymethane,dimethoxymethane or trioxane are corrosive. Rates of oxidation of thethree new fuels are comparable to, or better than, oxidation rates ofconventional organic fuels. For example, rates of oxidation fordimethoxymethane are higher than that of methanol, at the sametemperature. Trioxane achieves oxidation rates comparable to that offormaldehyde. However, trioxane has a much higher molecular weight thanformaldehyde and, as such, molecules of trioxane do not cross-over tothe cathode of the fuel cell as easily as molecules of formaldehyde.

[0030] Trimethoxymethane, dimethoxymethane and trioxane may be employedin a fuel cell having any of the improvements set forth above. However,the improved fuels may also be advantageously used within other organicfuel cells, including entirely conventional fuel cells.

[0031] Hence the various general objects of the invention set forthabove are achieved. Other objects and advantages of the invention willbe apparent from the detailed description set forth below.

BRIEF DESCRIPTION OF DRAWINGS

[0032] The objects and advantages of the present invention will becomemore readily apparent after reviewing the following detailed descriptionand accompanying drawings, wherein:

[0033]FIG. 1 provides a schematic representation of an improved liquidfeed organic fuel cell having a solid polymeric membrane configured inaccordance with a preferred embodiment of the invention.

[0034]FIG. 2 provides a schematic representation of a multi-cell fuelsystem employing the improved liquid feed organic fuel cell of FIG. 1.

[0035]FIG. 3 is a graph illustrating the performance of a solidpolymeric membrane electrolyte and a sulfuric acid electrolyte in liquidorganic fuels.

[0036]FIG. 4 is a graph illustrating the performance of liquid feed fuelcell of FIG. 1 for methanol/air and methanol/oxygen combinations.

[0037]FIG. 5 is a graph illustrating the effect of fuel concentration onthe performance of the liquid feed fuel cell of FIG. 1.

[0038]FIG. 6 is a graph illustrating the polarization behavior of thefuel electrode and cathode in the fuel cell of FIG. 1.

[0039]FIG. 7 is a block diagram illustrating a method for fabricatingelectrode containing hydrophilic proton-conducting ionomer additive foruse in liquid feed cells.

[0040]FIG. 8 is a graph illustrating the polarization characteristicsfor methanol oxidation at electrodes containing the ionomer additive andprepared in accordance with the procedure shown in FIG. 7.

[0041]FIG. 9 is a block diagram illustrating a method for fabricating anelectrode employing perfluorooctanesulfonic acid within anelectro-deposition bath.

[0042]FIG. 10 is a schematic illustration of an electrochemical cell foruse in performing the method of FIG. 9.

[0043]FIG. 11 is a illustrating polarization curves for an electrodefabricating using the method of FIG. 9.

[0044]FIG. 12 is a graph illustrating polarization curves of a fuel cellusing a sulfuric acid electrolyte and employing perfluorooctanesulfonicacid as a fuel additive.

[0045]FIG. 13 is a graph illustrating polarization curves of a fuel cellusing dimethoxymethane as a fuel for various fuel concentration levelswithin a half cell having a sulfuric acid electrolyte.

[0046]FIG. 14 is a graph illustrating polarization curves of a fuel cellusing dimethoxymethane as a fuel for differing temperatures andconcentrations within a half cell having a sulfuric acid electrolyte.

[0047]FIG. 15 is a graph illustrating cell voltage as a function ofcurrent density for the fuel cell of FIG. 1 using dimethoxymethane as afuel.

[0048]FIG. 16 is a graph illustrating polarization curves of a fuel cellusing trimethoxymethane as a fuel for various fuel concentration levelswithin a half cell having a sulfuric acid electrolyte.

[0049]FIG. 17 is a graph illustrating polarization curves of a fuel cellusing trimethoxymethane as a fuel for differing temperatures andconcentrations within a half cell having a sulfuric acid electrolyte.

[0050]FIG. 18 is a graph illustrating cell voltage as a function ofcurrent density for the fuel cell of FIG. 1 using trimethoxymethane ormethanol as a fuel.

[0051]FIG. 19 is a graph illustrating polarization curves of a fuel cellusing trioxane as a fuel for various fuel concentration levels within ahalf cell having a two molar sulfuric acid electrolyte.

[0052]FIG. 20 is a graph illustrating polarization curves of a fuel cellusing trioxane as a fuel for differing temperatures and concentrationsof sulfuric acid electrolyte within a half cell.

[0053]FIG. 21 is a graph illustrating cell voltage as a function ofcurrent density for the fuel cell of FIG. 1 using trioxane as fuel.

DETAILED DESCRIPTION OF THE INVENTION

[0054] Referring to the figures, the preferred embodiments of theinvention will now be described. Initially, an improved liquid feedorganic fuel Cell using a solid polymeric electrolyte membrane and aionomeric anode additive is described, primarily with reference to FIGS.1-6. Then, a method for fabricating the anode having the ionomericadditive is described with reference to FIGS. 7-8. A method forachieving improved wetting by fabricating an electrode within a bathcontaining perfluorooctanesulfonic acid is described with reference toFIGS. 9-11. A fuel cell employing perfluorooctanesulfonic acid as a fueladditive is described with reference to FIG. 12. Fuel cells employingdimethoxymethane, trimethoxymethane and trioxane as fuels are describedwith reference to FIGS. 13-21.

[0055] Fuel Cell Employing Solid Proton Conducting Elecrolyte Membrane

[0056]FIG. 1 illustrates a liquid feed organic fuel cell 10 having ahousing 12, an anode 14, a cathode 16 and a solid polymerproton-conducting cation-exchange electrolyte membrane 18. As will bedescribed in more detail below, anode 14, cathode 16 and solid polymerelectrolyte membrane 18 are preferably a single multi-layer compositestructure, referred to herein as a membrane electrode assembly. A pump20 is provided for pumping an organic fuel and water solution into ananode chamber 22 of housing 12. The organic fuel and water mixture iswithdrawn through an outlet port 23 and is re-circulated through are-circulation system described below with reference to FIG. 2 whichincludes a methanol tank 19. Carbon dioxide formed in the anodecompartment is vented through a port 24 within tank 19. An oxygen or aircompressor 26 is provided to feed oxygen or air into a cathode chamber28 within housing 12. FIG. 2, described below, illustrates a fuel cellsystem incorporating a stack of individual fuel cells including there-circulation system. The following detailed description of the fuelcell of FIG. 1 primarily focuses on the structure and function of anode14, cathode 16 and membrane 18.

[0057] Prior to use, anode chamber 22 is filled with the organic fueland water mixture and cathode chamber 28 is filled with air or oxygen.During operation, the organic fuel is circulated past anode 14 whileoxygen or air is pumped into chamber 28 and circulated past cathode 16.When an electrical load (not shown) is connected between anode 14 andcathode 16, electro-oxidation of the organic fuel occurs at anode 14 andelectro-reduction of oxygen occurs at cathode 16. The occurrence ofdifferent reactions at the anode and cathode gives rise to a voltagedifference between the two electrodes. Electrons generated byelectro-oxidation at anode 14 are conducted through the external load(not shown) and are ultimately captured at cathode 16. Hydrogen ions orprotons generated at anode 14 are transported directly across membraneelectrolyte 18 to cathode 16. Thus, a flow of current is sustained by aflow of ions through the cell and electrons through the external load.

[0058] As noted above, anode 14, cathode 16 and membrane 18 form asingle composite layered structure. In a preferred implementation,membrane 18 is formed from Nafion™, a perfluorinated proton-exchangemembrane material. Nafion™ is a co-polymer of tetrafluoroethylene andperfluorovinylether sulfonic acid. Other membrane materials can also beused. For example, membranes of modified perflourinated sulfonic acidpolymer, polyhydrocarbon sulfonic acid and composites of two or morekinds of proton exchange membranes can be used.

[0059] Anode 14 is formed from platinum-ruthenium alloy particles eitheras fine metal powders, i.e. “unsupported”, or dispersed on high surfacearea carbon, i.e. “supported”. The high surface area carbon may be amaterial such as Vulcan XC-72A, provided by Cabot Inc., USA. A carbonfiber sheet backing (not shown) is used to make electrical contact withthe particles of the electrocatalyst. Commercially available Toray™paper is used as the electrode backing sheet. A supported alloyelectrocatalyst on a Toray™ paper backing is available from E-Tek, Inc.,of Framingham, Mass. Alternately, both unsupported and supportedelectrocatalysts may be prepared by chemical methods, combined withTeflon™ binder and spread on Toray™ paper backing to produce the anode.An efficient and time-saving method of fabrication of electro-catalyticelectrodes is described in detail herein below.

[0060] Platinum-based alloys in which a second metal is either tin,iridium, osmium, or rhenium can be used instead of platinum-ruthenium.In general, the choice of the alloy depends on the fuel to be used inthe fuel cell. Platinum-ruthenium is preferable for electro-oxidation ofmethanol. For platinum-ruthenium, the loading of the alloy particles inthe electrocatalyst layer is preferably in the range of 0.5-4.0 mg/cm².More efficient electro-oxidation is realized at higher loading levels,rather than lower loading levels.

[0061] Cathode 16 is a gas diffusion electrode in which platinumparticles are bonded to one side of membrane 18. Cathode 16 ispreferably formed from unsupported or supported platinum bonded to aside of membrane 18 opposite to anode 14. Unsupported platinum black(fuel cell grade) available from Johnson Matthey Inc., USA or supportedplatinum materials available from E-Tek Inc., USA are suitable for thecathode. As with the anode, the cathode metal particles are preferablymounted on a carbon backing material. The loading of the electrocatalystparticles onto the carbon backing is preferably in the range of 0.5-4.0mg/cm². The electrocatalyst alloy and the carbon fiber backing contain10-50 weight percent Teflon™ to provide hydrophobicity needed to createa three-phase boundary and to achieve efficient removal of waterproduced by electro-reduction of oxygen.

[0062] During operation, a fuel and water mixture (containing no acidicor alkaline electrolyte) in the concentration range of 0.5-3.0mole/liter is circulated past anode 14 within anode chamber 22.Preferably, flow rates in the range of 10-500 milliliters/min. are used.As the fuel and water mixture circulates past anode 14, the followingelectrochemical reaction, for an exemplary methanol cell, occursreleasing electrons:

Anode: CH₃OH+H₂O→CO₂+6H⁺+6e⁻  (1)

[0063] Carbon dioxide produced by the above reaction is withdrawn alongwith the fuel and water solution through outlet 23 and separated fromthe solution in a gas-liquid separator (described below with referenceto FIG. 2). The fuel and water solution is then re-circulated into thecell by pump 20.

[0064] Simultaneous with the electrochemical reaction described inequation 1 above, another electrochemical reaction involving theelectro-reduction of oxygen, which captures electrons, occurs at cathode16 and is given-by:

Cathode: O₂+4H⁺+4e⁻→H₂O  (2)

[0065] The individual electrode reactions described by equations 1 and 2result in an overall reaction for the exemplary methanol fuel cell givenby:

Cell: CH₃OH+1.50₂→CO₂+2H₂O  (3)

[0066] At sufficiently high concentrations of fuel, current densitiesgreater than 500 mA/cm can be sustained. However, at theseconcentrations, a crossover rate of fuel across membrane 18 to cathode16 increases to the extent that the efficiency and electricalperformance of the fuel cell are reduced significantly. Concentrationsbelow 0.5 mole/liter restrict cell operation to current densities lessthan 100 mA/cm2. Lower flow rates have been found to be applicable atlower current densities. High flow rates are required while operating athigh current densities to increase the rate of mass transport of organicfuel to the anode as well as to remove the carbon dioxide produced byelectrochemical reaction. Low flow rates also reduce the crossover ofthe fuel from the anode to the cathode through the membrane.

[0067] Preferably, oxygen or air is circulated past cathode 16 atpressures in the range of 10 to 30 psig. Pressures greater than ambientimprove the mass transport of oxygen to the sites of electrochemicalreactions, especially at high current densities. Water produced byelectrochemical reaction at the cathode is transported out of cathodechamber 28 by flow of oxygen through port 30.

[0068] In addition to undergoing electro-oxidation at the anode, theliquid fuel which is dissolved in water permeates through solid polymerelectrolyte membrane 18 and combines with oxygen on the surface of thecathode electrocatalyst. This process is described by equation 3 for theexample of methanol. This phenomenon is termed “fuel crossover”. Fuelcrossover lowers the operating potential of the oxygen electrode andresults in consumption of fuel without producing useful electricalenergy. In general, fuel crossover is a parasitic reaction which lowersefficiency, reduces performance and generates heat in the fuel cell. Itis therefore desirable to minimize the rate of fuel crossover. The rateof crossover is proportional to the permeability of the fuel through thesolid electrolyte membrane and increases with increasing concentrationand temperature. By choosing a solid electrolyte membrane with low watercontent, the permeability of the membrane to the liquid fuel can bereduced. Reduced permeability for the fuel results in a lower crossoverrate. Also, fuels having a large molecular size have a smaller diffusioncoefficient than fuels which have small molecular size. Hence,permeability can be reduced by choosing a fuel having a large molecularsize. While water soluble fuels are desirable, fuels with moderatesolubility exhibit lowered permeability. Fuels with high boiling pointsdo not vaporize and their transport through the membrane is in theliquid phase. Since the permeability for vapors is higher than liquids,fuels with high boiling points generally have a low crossover rate. Theconcentration of the liquid fuel can also be lowered to reduce thecrossover rate. With an optimum distribution of hydrophobic andhydrophilic sites, the anode structure is adequately wetted by theliquid fuel to sustain electrochemical reaction and excessive amounts offuel are prevented from having access to the membrane electrolyte. Thus,an appropriate choice of anode structures can result in the highperformance and desired low crossover rates.

[0069] Because of the solid electrolyte membrane is permeable to waterat temperatures greater than 60° C., considerable quantities of waterare transported across the membrane by permeation and evaporation. Thewater transported through the membrane is condensed in a water recoverysystem and fed into a water tank (both described below with reference toFIG. 2) so that the water can be re-introduced into anode chamber 22.

[0070] Protons generated at anode 14 and water produced at cathode 16are transported between the two electrodes by proton-conducting solidelectrolyte membrane 18. The maintenance of high proton conductivity ofmembrane 18 is important to the effective operation of an organic/airfuel cell. The water content of the membrane is maintained by providingcontact directly with the liquid fuel and water mixture. The thicknessof the proton-conducting solid polymer electrolyte membranes should bein the range from 0.05-0.5 mm to be dimensionally stable. Membranesthinner than 0.05 mm may result in membrane electrode assemblies whichare poor in mechanical strength, while membranes thicker than 0.5 mm maysuffer extreme and damaging dimensional changes induced by swelling ofthe polymer by the liquid fuel and water solutions and also exhibitexcessive resistance. The ionic conductivity of the membranes should begreater than 1 ohm⁻¹ cm⁻¹ for the fuel cell to have a tolerable internalresistance. As noted above, the membrane should have a low permeabilityto the liquid fuel. Although a Nafion™ membrane has been found to beeffective as a proton-conducting solid polymer electrolyte membrane,perfluorinated sulfonic acid polymer membranes such as Aciplex™(manufactured by Asahi Glass Co., Japan) and polymer membranes made byDow Chemical Co., USA, such as XUS13204.10 which are similar inproperties to Nafion™ are also applicable. Membranes of polyethylene andpolypropylene sulfonic acid, polystyrene sulfonic acid and otherpolyhydrocarbon-based sulfonic acids (such as membranes made by RAICorporation, USA) can also be used depending on the temperature andduration of fuel cell operation. Composite membranes consisting of twoor more types of proton-conducting cation-exchange polymers withdiffering acid equivalent weights, or varied chemical composition (suchas modified acid group or polymer backbone), or varying water contents,or differing types and extents of cross-linking (such as cross linked bymultivalent cations e.g., Al 3+, Mg 2+ etc.,) can be used to achieve lowfuel permeability. Such composite membranes can be fabricated to achievehigh ionic conductivity, low permeability for the liquid fuel and goodelectrochemical stability.

[0071] As can be appreciated for the foregoing description, a liquidfeed direct oxidation organic fuel cell is achieved using aproton-conducting solid polymer membrane as electrolyte without the needfor a free soluble acid or base electrolyte. The only electrolyte is theproton-conducting solid polymer membrane. No acid is present in freeform in the liquid fuel and water mixture. Since no free acid ispresent, acid-induced corrosion of cell components, which can occur incurrent-art acid based organic/air fuel cells, is avoided. This offersconsiderable flexibility in the choice of materials for the fuel celland the associated subsystems. Furthermore, unlike fuel cells whichcontain potassium hydroxide as liquid electrolyte, cell performance doesnot degrade because soluble carbonates are not formed. Also by the useof a solid electrolyte membrane, parasitic shunt currents are avoided.

[0072] Referring now to FIG. 2, a fuel cell system employing a stack offuel cells similar to the fuel cell shown in FIG. 1 will now bedescribed. The fuel cell system includes a stack 25 of fuel cells, eachhaving the membrane/electrode assembly described above with reference toFIG. 1. Oxygen or air is supplied by an oxidant supply 26 which may be,for example, a bottled oxygen supply, an air-blowing fan or an aircompressor. An air and water or oxygen and water mixture is withdrawnfrom stack 25 through an outlet port 30 and conveyed to a water recoveryunit 27. Water recovery unit 27 operates to separate the air or oxygenfrom the water. A portion of the air or oxygen separated by unit 27 isreturned to oxidant supply 26 for re-entry into stack 25. Fresh air oroxygen is added to supply 27. Water separated by unit 27 is fed to afuel and water injection unit 29 which also receives an organic fuel,such as methanol, from a storage tank 33. Injection unit 29 combines thewater from recovery unit 27 with the organic fuel from tank 33, yieldinga fuel and water solution with the fuel dissolved in the water.

[0073] The fuel and water solution provided by injection unit 29 is fedinto a circulation tank 35. A fuel and water mixture containing carbondioxide is withdrawn through port 23 from stack 25 and is fed through aheat exchanger 37 and into circulation tank 35. Hence circulation tank35 receives both a fuel and water solution from injection unit 29 and afuel and water solution containing a carbon dioxide gas from heatexchanger 37. Circulation tank 35 extracts carbon dioxide from the fueland water mixture and releases the carbon dioxide through a vent 39. Theresulting fuel and water solution is fed through pump 20 and into stack25. Circulation tank 35 can also be located between stack 25 and heatexchanger 34 so as to remove the carbon dioxide before the heatexchanger and thereby improve performance of the heat exchanger.

[0074] The operation of the various components illustrated in FIG. 2will now be described in greater detail. Circulation tank 35 is a towerhaving a large head space. The liquid fuel and water mixture receivedfrom injection unit 29 is added into a top of the tower. The fuel andwater mixture having carbon dioxide therein is fed into a bottom portionof the tower. Carbon dioxide gas released from the fuel and watermixture is allowed to accumulate in the head space and is ultimatelyvented. Alternately, the fuel and water mixture containing the carbondioxide can be passed through a cluster of tubes of a microporousmaterial such as Celgard™ or GoreTex™ which allows gases to be releasedthrough walls of the tubes of the microporous material, while the liquidfuel flows along an axis of the tubes. Celgard™ and GoreTex™ areregistered trademarks of Celanese Corp. and Gore Association, USA.

[0075] A static re-circulation system (not shown) can be employed withinan anode chamber of stack 25 to separate carbon dioxide from the fueland water mixture such that an external circulation tank need not beprovided. With such a system, bubbles of carbon dioxide, due to innatebuoyancy, tend to rise vertically within the anode chamber: Viscousinteraction with the liquid fuel mixture surrounding the gas bubblesdrags the liquid fuel upwards in the direction of outlet port 23. Onceoutside the anode chamber, the liquid releases the gas, exchanges heatwith the surroundings and cools, thereby becoming denser than the liquidin the cell. The denser liquid is fed into the bottom of the anodechamber through an inlet port. Instead of expending electrical energy onthe pump, the static re-circulation system takes advantage of the heatand gas produced in the cell. The aforementioned process forms the basisof the static re-circulation system which will not be described infurther detail. It should be noted that the use of a staticre-circulation system may restrict the orientation at which the fuelcell can be operated and may be viable only for stationary applications.

[0076] Test results for fuel cell having a Nafion™ electrolyte membrane

[0077] The kinetics of electro-oxidation of methanol for a sulfuric acidelectrolyte and Nafion™ electrolyte have been studied by galvanostaticpolarization measurements in electrochemical cells (not illustrated butsimilar to an electro-deposition cell illustrated below in FIG. 10). Thecells consist of a working electrode, a platinum counter electrode and areference electrode. The working electrode is polarized within asolution containing the chosen electrolyte and liquid fuel. Thepotential of the working electrode versus the reference electrode ismonitored.

[0078]FIG. 3 illustrates the polarization curve, i.e. polarizationversus current density in milliampers/cm² (mA/cm²), for the kinetics ofmethanol oxidation in the Nafion™ and sulfuric acid electrolytes, withcurve 41 illustrating polarization for 0.5M sulfuric acid electrolyteand with curve 43 illustrating polarization for a Nafion™ electrolyte.Polarization is represented in potential versus NHE, wherein NHE standsfor normalized hydrogen electrode. The curves represent measured datafor a fuel consisting of a 1M mixture of methanol in water at 60° C. Ascan be seen from FIG. 3, the polarization losses are lower when theelectrode is in contact with Nafion™ rather than sulfuric acid. Hence,it can be concluded that the kinetics of electro-oxidation of methanolare more facile when the electrolyte is Nafion™. These observations maybe explained by the fact that strong adsorption of sulfate ions occursat an electrode/sulfuric acid interface at positive potentials whichhinders the kinetics of electro-oxidation. Such adsorption does notoccur when Nafion™ is employed as an electrolyte since no such ions areproduced. Also, it is believed that the kinetics of electro-reduction ofoxygen or air are enhanced at an electrode/Nafion™ interface, incomparison to an electrode/sulfuric acid interface. This later effectmay be due to the higher solubility of oxygen in Nafion™ and the absenceof strongly adsorbed anions. Therefore, the use of the proton-conductingsolid polymer membrane as electrolyte is beneficial to the kinetics ofboth of the electrode reactions and overcomes the disadvantages of asulfuric acid electrolyte.

[0079] Also, sulfuric acid electrolytes suffer degradation attemperatures greater than 80° C. Products of degradation can reduce theperformance of the individual electrodes. The electrochemical stabilityand thermal stability of a solid polymer electrolyte such as Nafion™ isconsiderably higher than that of sulfuric acid and the solid polymerelectrolyte can be used at temperatures as high as 120° C. Therefore theuse of the proton-conducting solid polymer membrane permits long termfuel cell operation at temperatures as high as 120° C., which providesan additional advantage since the kinetics of electro-oxidation of fuelsand electro-reduction of oxygen occur with greater facility as thetemperature is increased.

[0080]FIG. 4 illustrates the performance of the fuel cell shown in FIG.2 when operated at 65° C. for both a methanol oxygen combination and amethanol/air combination. In FIG. 4, voltage of the fuel cell isillustrated along axis 32 and current density in mA/cm² is illustratedalong axis 34. Curve 36 indicates performance of the methanol/oxygencombination while curve 38 illustrates performance of the methanol/aircombination. As can be seen, the use of pure oxygen provides slightlybetter performance than air.

[0081]FIG. 5 illustrates the effect of fuel concentration on cellperformance. Fuel cell potential is illustrated along axis 40 whilecurrent density in mA/cm² is illustrated along axis 42. Curve 44indicates performance for a 2.0 molar methanol solution at 150 degreesFahrenheit(F). Curve 46 illustrates performance for a 0.5 molar methanolmixture at 140 degrees F. Curve 48 illustrates performance for a 4.0Mmethanol mixture at 160 degrees F. As can be seen, the 2.0M methanolmixture provides the best overall performance. Also, FIG. 5 illustratesthat the fuel cell can sustain current densities as high as 300 mA/cm²while maintaining reasonably high voltage. In particular, the 2.0 molarmethanol mixture provides a voltage of over 0.4 volts at nearly 300mA/cm². The performance illustrated in FIG. 5 represents a significantimprovement over the performance of previous organic fuel cells.

[0082] Polarization behavior of the anode and cathode of the fuel cellare illustrated in FIG. 6 as a function of current density in mA/cm²,with voltage shown along axis 50 and current density along axis 52.Curve 54 illustrates polarization behavior for a 2.0 molar mixture at150 degrees F. Curve 56 illustrates the polarization behavior for thefuel while curve 58 separately illustrates polarization behavior for theoxygen.

[0083] Anode structures for Liquid Feed Fuel Cells

[0084] The anode structure for liquid feed fuel cells must be quitedifferent from that of conventional fuel cells. Conventional fuel cellsemploy gas diffusion type electrode structures that can provide gas,liquid and solid equilibrium. However, liquid feed type fuel cellsrequire anode structures that are similar to batteries. The anodestructures must be porous and must be capable of wetting the liquidfuel. In addition, the structures must have both electronic and ionicconductivity to effectively transport electrons to the anode currentcollector (carbon paper) and hydrogen/hydronium ions to the Nafion™electrolyte membrane. Furthermore, the anode structure must help achievefavorable gas evolving characteristics at the anode.

[0085] Electrodes required for liquid feed type fuel cells can befabricated specifically or conventional gas diffusion electrodesavailable commercially can be modified with suitable additives.

[0086] Electrode Impregnation with Ionomeric Additive

[0087] The electrocatalyst layer and carbon fiber support of anode 14(FIG. 1) are preferably impregnated with a hydrophilic proton-conductingpolymer additive such as Nafion™. The additive is provided within theanode, in part, to permit efficient transport of protons and hydroniumproduced by the electro-oxidation reaction. The ionomeric additive alsopromotes uniform wetting of the electrode pores by the liquid fuel/watersolution and provides for better utilization of the electrocatalyst. Thekinetics of methanol electro-oxidation by reduced adsorption of anionsis also improved. Furthermore, the use of the ionomeric additive helpsachieve favorable gas evolving characteristics for the anode.

[0088] For an anode additive to be effective, the additive should behydrophilic, proton-conducting, electrochemically stable and should nothinder the kinetics of oxidation of liquid fuel. Nafion™ satisfies thesecriteria and is a preferred anode additive. Other hydrophilicproton-conducting additives which are expected to have the same effectas Nafion™, are montmorrolinite clays, zeolites, alkoxycelluloses,cyclodextrins, and zirconium hydrogen phosphate.

[0089]FIG. 7 is a block diagram which illustrates the steps involved inimpregnation of the anode with an ionomeric additive such as Nafion™.Initially, a carbon electrode structure is obtained or prepared.Commercially available high surface area carbon electrode structureswhich employ a mixture of high surface area electrocatalyst and Teflon™binder applied on Toray™ carbon fiber paper may be used. Anelectro-catalytic electrode may also be prepared from high surface areacatalyst particles and Toray™ paper, both available from E-Tek, Inc.,using TFE-30™, an emulsion of polytetrafluoroethylene. Although thesestructures can be prepared from the foregoing component materials,prefabricated structures may also be obtained directly from E-Tek in anydesired dimension.

[0090] At step 302, the electrodes are impregnated with an ionomericadditive, such as Nafion™, by immersing the electrocatalyst particles ina solution containing 0.5-5% of the ionomeric additive (by appropriatedilution, with methanol or isopropanol, of solutions supplied by AldrichChemical Co., or Solution Technologies Inc.) for 5-10 minutes. Theelectrode is then removed, at step 304, from the solution and dried inair or vacuum at temperatures ranging from 20-60° C. to volatilize anyhigher alcohol residues associated with the Nafion™ solution. Theimpregnation steps 302-304 are repeated until the desired composition(which is in the range of 2-10% of the weight of the electrocatalyst) isachieved. A loading of 0-1 to 0.5 mg/cm² is exemplary. Electrodecompositions with additive in excess of 10% may result in an increasedinternal resistance of the fuel cell and poor bonding with the solidpolymer electrolyte membrane. Compositions with less than 2% of theadditives do not typically result in improved electrode performance.

[0091] To form impregnated electrodes from electrocatalyst particles,the electrocatalyst particles are mixed in with a solution of Nafion™diluted to 1% with isopropanol. Then the solvent is allowed to evaporateuntil a thick mix is reached. The thick mix is then applied onto aToray™ paper to form a thin layer of the electrocatalyst. A mixture ofabout 200 meter²/gram high surface area particles applied to the Toray™paper is exemplary. Note here that the electrocatalyst layer so formedhas only Nafion™ and no Teflon™. Electrodes so prepared are then driedin a vacuum at 60° C. for 1 hour to remove higher alcohol residues,after which they are ready for use in liquid feed cells.

[0092] A commercially available high-surface area platinum-tin electrodewas impregnated with Nafion™ according to the procedure described above.FIG. 8 compares the performance of a Nafion™ impregnated electrode witha non-impregnated electrode as measured within a half cell similar tothe cell of FIG. 10 (below) but containing a sulfuric acid electrolyte.In particular, FIG. 8 illustrates the polarization measurements inliquid formaldehyde fuel (1 molar) with sulfuric acid electrolyte (0.5molar). The current density in mA/cm² is illustrated along axis 306 andthe potential in volts along axis 308. Curve 310 is the galvanostaticpolarization curve for a platinum-tin electrode that does not includeNafion™. Curve 312 is the galvanostatic polarization curve for aplatinum-tin electrode not impregnated with Nafion™.

[0093] It can be seen from FIG. 8 that far greater current densities areachieved with the Nafion™-impregnated electrode than with thenon-impregnated electrode. Indeed with the non-impregnated electrode,very little oxidation of formaldehyde occurs. The addition of Nafion™thus provides a dramatic improvement. In addition, the absence of anyhysteresis in the galvanostatic polarization curves suggest that thesecoatings are stable.

[0094] What has been described thus far is an improved liquid feed fuelcell anode impregnated with an ionomeric additive. A method forfabricating the anode to include the ionomeric additive has also beendescribed. The remaining sections of the Detailed Description provide adescription of the use of perfluorooctanesulfonic acid as an additivewithin an electrodeposition bath used for fabricating electrodes and asa direct additive within a fuel. New fuels-are also described.

[0095] Electro-deposition of Electrodes using PerfluorooctanesulfonicAcid Additive

[0096] With reference to FIGS. 9-11, a method for fabricating anelectrode for use in a organic fuel cell will now be described indetail. The method is advantageously employed for fabricating a cathodefor use in the liquid organic fuel cell described above. However,electrodes prepared by the method of FIGS. 9-11 may alternatively beused in a variety of organic fuel cells.

[0097] Referring first to FIG. 9, the steps of a method for fabricatingthe anode will now be described. Initially, at 200, a carbon electrodestructure is prepared by applying a mixture of high-surface-area carbonparticles and a Teflon™ binder to a fiber-based carbon paper.Preferably, the carbon particles have a surface area of 200 meters²/gram(m²/g). A suitable carbon particle substrate, referred to Vulcan XC-72,is available from E-Tek Inc. The Teflon™ binder is preferably added toachieve a percentage, by weight, of 15%. The fiber based carbon paper ispreferably Toray™ paper, also available from E-Tek Incorporated. Thecarbon structure may be prepared from the forgoing component materials.Alternatively, commercial prefabricated structures are available in 2inch by 2 inch squares directly from E-Tek Inc.

[0098] At Step 202, an electro-deposition bath is prepared by dissolvinghydrogen hexachloropaltinate (IV) and potassium pentachloroaquoruthonium(III) within sulfuric acid. Preferably, the resultingmetal-ion-concentration is within the range of 0.01-0.05M. Also,preferably, the sulfuric acid has the concentration of 1M. The forgoingcompound is employed for obtaining platinum-ruthenium deposits on thecarbon electrode structure. Alternative solutions may be employed. Forexample, to obtain platinum-tin deposits, a stannic chloride compound isdissolved in a sulfuric acid instead.

[0099] The metallic ion salts are dissolved in the sulfuric acidprimarily to prevent hydrolysis of the solution. For rutheniumdeposition, the resulting solution is preferably de-aerated to preventthe formation of higher oxidation states.

[0100] High purity perfluoroctanesulfonic acid (C-8 acid) is added tothe bath at step 204. C-8 acid is preferably added to a concentration ina range of 0.1-1.0 grams/liters. C-8 acid is provided to facilitatecomplete wetting of the carbon particles. C-8 acid is electro-inactiveand does not specifically adsorb at metal sites within the structure.Therefore, C-8 acid is innocuous to subsequent electro-depositionprocesses. The addition of C-8 acid has been found to be highlybeneficial, and perhaps necessary for successful electro-deposition ontothe electrodes.

[0101] At 206, the carbon electrode structure resulting from step 200 isplaced within the electro-deposition bath resulting from step 204. Aplatinum anode is also positioned within the bath. For the deposition ofother metal ions, an alternate anode material may be employed.

[0102] A voltage is then applied between the carbon electrode structureand the platinum anode at step 208. The voltage is applied for about 5to 10 minutes to achieve electro-deposition of platinum-ruthenium ontothe carbon electrode to a loading of about 5 mg/cm². Preferably, avoltage of approximately −0.8V vs mercury sulfate reference electrode isapplied.

[0103] After a desired amount of metal is deposited onto the carbonelectrode, the electrode is removed, at step 210, and washed indeionized water. Preferably, the electrode is washed at least threetimes in circulating de-ionized water for 15 minutes each time. Thewashing step is provided primarily to rid the surface of the carbonelectrode of absorbed chloride and sulfate ions. The washing step hasbeen found to be highly desirable, and perhaps necessary, for yieldingan effective electrode for use in an organic fuel cell.

[0104] Electrodes, resulting from the fabrication method of step 206,have been found to have very uniform “cotton-ball”-shaped particles,with a significant amount of fine structure. Average particle sizehas-been found to be on the order of 0.1 microns.

[0105] A deposition setup for use in implementing the method of FIG. 9is illustrated in FIG. 10. Specifically, FIG. 10 illustrates athree-electrode cell 212 which includes a single carbon-structureelectrode 214, a pair of platinum counter-electrodes (or anodes) 216 anda reference electrode 218. All electrodes are positioned within a bath220 formed of the aforementioned metallic/C-8 acid solution. Electricalcontacts 222 and 224 are positioned on interior side surfaces of cell212 above bath 220. A magnetic stirrer 226 is positioned within bath 220to facilitate stirring the bath.

[0106] Adequate electro-deposition typically occurs within a period offive to ten minutes, depending upon the operating conditions and thecatalyst loading desired.

[0107] The monitoring equipment for use in monitoring and controllingthe electrode potential are not illustrated in FIG. 10 as the functionand operation of such devices are well known to those skilled in theart.

[0108]FIG. 11 illustrates the performance of an exemplary electrodedeposited using the method of FIG. 9 within the electro-deposition cellof FIG. 7. In FIG. 11, potential in volts versus NHE is provided alongaxis 240 whereas current density in mA/cm² is provided along axis 242.Curve 246 illustrates the galvanostatic polarization curve for acarbon-supported platinum-ruthenium alloy electrode prepared inaccordance with the forgoing for a loading of 5 mg/cm². Curve 246illustrates galvanostatic polarization for an electrode having a 1mg/cm² loading. In each case, the electrode was employed within asulfuric acid electrolye in a half-cell. The fuel cell included anorganic fuel composed of 1 molar methanol and 0.5 molar sulfuric acid,operated at 60° C. At the loading of 5 mg/cm², the electrode sustains acontinuous current density of 100 mA/cm² at 0.45 volts versus NHE.

[0109] The results illustrated in FIG. 11 are exemplary of performancewhich may be achieved using an electrode fabricated in accordance withthe method of FIG. 9. Further performance enhancement may be achievedwith appropriate optimization of the electro-deposition conditions andthe alloy composition. Hence, the particular conditions andconcentrations described above are not necessarily optimal but merelyrepresent a currently known best mode for fabricating electrodes.

[0110] Perfluoroctanesulfonic Acid (C-8 Acid) as a Fuel Additive

[0111] The use of C-8 acid as an additive within an electrodepositionbath was described above. It has also been determined that C-8 acid maybe advantageously applied as an additive within the fuel of a liquidfeed fuel cell employing a sulfuric acid electrolyte. In particular, ithas been found that straight chain C-8 acid, having the molecularformula C₈F₁₇SO₃H, in concentrations from 0.001 to 0.1M is an excellentwetting agent within a liquid feed fuel cell.

[0112] FIGS. 12 illustrates results of experiments which contrast theuse of C-8 acid as an additive with fuel cells lacking the additive. Inparticular, FIG. 12 illustrates the results of half-cell experimentsusing a Teflon™ coated high-surface area carbon-supported platinum andplatinum alloy electrode mounted within a sulfuric acid electrolyte. Theresults wee obtained using a half-cell similar to the cell illustratedin FIG. 10. FIG. 12 illustrates potential versus NHE along the verticalaxis 400 and current density in mA/cm² along a horizontal axis 402. Fourcurves are provided illustrating polarization for a fuel containing noadditive (curve 404), 0.0001M additive (curve 406), 0.001M additive(curve 408) and 0.01M additive (curve 412).

[0113] As can be seen from FIG. 12, the addition of the C-8 additivedecreases the polarization rather significantly. Although not shown, theoxidation of methanol has also been investigated using 0.1M pure C-8acid solutions without any sulfuric acid. Polarization curves (notshown) indicate that the kinetics are not effected by the presence ofthe perfluorooctanesulfonic ion.

[0114] Thus, FIG. 12 demonstrates that the use of C8 acid as an additivein the concentration range 0-001M or greater is beneficial to liquidfuel solutions when employing commercially available Teflon™ coated fuelcell electrodes, at least for fuel cells employing sulfuric acid askelectrolyte.

[0115] With reference to the remaining figures, three new fuels for usein liquid feed fuel cells are described. The fuels are dimethoxymethane,trimethoxymethane, and trioxane.

[0116] Dimethoxymethane as a fuel for a liquid feed fuel cell

[0117] FIGS. 13 -15 illustrate the results of experiments conductedusing dimethoxymethane (DMM)as a fuel for an organic direct liquid feedfuel cell. In use, DMM is mixed with water to a concentration in therange of about 0.1 to 2M and fed into a fuel cell. Other concentrationsmay also be effective. The fuel cell may be of conventional design ormay include one or more of the improvements described above. Within thefuel cell, the DMM is electro-oxidized at the anode of the cell. Theelectro-oxidation of DMM involves a series of dissociative stepsfollowed by surface reaction to form carbon dioxide and water.

[0118] The electrochemical reaction is given by:

(CH₃O)2CH₂+4H₂O→CO₂+16H⁺+16e⁻  (4)

[0119] Experiments testing the electro-oxidation of DMM have beenperformed in half cells of the similar to the cell shown in FIG. 10 withtemperature control using a 0.5M sulfuric acid electrolyte with Pt—Sn orPt—Ru electrocatalyst electrodes. The galvanostatic polarization curvesshown in FIG. 13 illustrate the electro-oxidation characteristics of DMMfor platinum-tin electrodes for several different fuel concentrations.The platinum-tin electrodes are of the gas-diffusion type consisting of0.5 mg/cm² total metal supported on Vulcan XC-72 obtained from Etek,Inc., Framingham, Mass. In FIG. 13, current density is illustrated alongaxis 500 and polarization (in terms of potential versus NHE) is providedalong axis 502. Curves 504, 506, 508 and 510, respectively, illustratepolarization for DMM concentrations of 0, 1M, 0.5M, 1M and 2M. FIG. 13shows that increased concentration improves the kinetics of oxidation ofDMM. The curves of FIG. 13 were measured in a half cell employing 0.5Msulfuric acid as an electrolyte, along with 0.1 M C-8 acid. Themeasurements were conducted at room temperature.

[0120] It has been found that DMM can be oxidized at potentialsconsiderably more negative than methanol. Also, temperature has beenfound to significantly influence the rates of oxidation. However, DMMhas a low boiling point of 41° C. Hence, difficulties may arise inattempting to use DMM in a liquid feed fuel cell for temperatures higherthan the boiling point.

[0121]FIG. 14 illustrates polarization for two different concentrationsat two different temperatures. Current density is provided along axis512 and polarization (in terms of potential v. NHE) is provided alongaxis 514. Curve 516 illustrates polarization for a 1M concentration ofDMM at room temperature. Curve 18 illustrates polarization for a 2Mconcentration of DMM at 55° C. As can be seen, improved polarization isachieved using a higher concentration at a higher temperature. Also, acomparison of curve 510 of FIG. 13 with curve 518 of FIG. 14 illustratesthat an increase in temperature yields an improved polarization for thesame concentration level. Hence, it is believed that an increase intemperature results in improved kinetics of electro-oxidation.

[0122] In addition to the half cell experiments illustrated in FIGS. 13and 14, fuel cell experiments were also conducted to verify theeffectiveness of DMM in a fuel cell. The direct oxidation of DMM in fuelcells was carried out in a liquid feed type fuel cell as illustratedabove in FIGS. 1 and 2. Hence, the fuel ceil employed a protonconducting solid polymer membrane (Nafion™ 117) as the electrolyte. Themembrane electrode assembly consisted of a fuel oxidation electrode madeof unsupported platinum-ruthenium catalyst layer (4 mg/cm²)andgas-diffusion type unsupported platinum electrode (4 mg/cm²)for thereduction of oxygen. The fuel cell used a 1M solution of DMM on the fueloxidation side and oxygen at 20 psi on the cathode.

[0123] Analysis of the oxidation products of DMM show only methanol.Methanol is considered a possible intermediate in the oxidation of DMMto carbon dioxide and water. However, since the fuel cell system iscompatible with methanol, the presence of methanol as an intermediate isnot a concern since the methanol is also ultimately oxidized to carbondioxide and water.

[0124] The current-voltage characteristics of a liquid feed directoxidation fuel cell using DMM as a fuel is shown in FIG. 15. The fuelcell was operated at 37° C. In FIG. 15, current density in mA/cm² isprovided along axis 520. Cell voltage in volts is provided along axis522. Curve 524 illustrates cell voltage as a function of current densityfor a 1M DMM solution described above. As can be seen from FIG. 15, thecell voltages reached 0.25 V at 50 nA/cm² with DMM which is as high asthat attained with methanol (not shown). By working at ahigher-temperature and using a Pt—Sn catalyst, even better performancemay be achieved. The low boiling point of DMM also makes it a candidatefor a gas-feed type operation.

[0125] Thus from these half-cell and full-cell measurements it has beenfound that DMM is capable of being oxidized at very high rates.Therefore, it is believed that DMM is an excellent fuel for use indirect oxidation fuel cells. Also, DMM is a non-toxic, low-vaporpressure liquid, permitting easy handling. In addition DMM can besynthesized from natural gas (methane) by conventional techniques.

[0126] Trimethoymethane as a fuel for a liquid feed fuel cell

[0127] FIGS. 16-18 illustrate the results of experiments conducted usingtrimethoxymethane (TMM) as a fuel for an organic direct liquid feed fuelcell. As with DMM described above, in use, TMM is mixed with water to aconcentration in the range of about 0.1 to 2M and fed into a fuel cell.Other concentrations may also be effective. The fuel cell may be ofconventional design or may include one or more of the improvementsdescribed above. Within the fuel cell, the TMM is electro-oxidized atthe anode of the cell. The electrochemical oxidation of TMM isrepresented by the following action:

(CH₃O)₃CH+5H₂O→4CO₂+20H⁺+20e⁻  (5)

[0128] Experiments verifying the electro-oxidation of TMM have beenperformed in half-cells similar to the cell shown in FIG. 10 withtemperature control using a Pt—Sn electrode with a 0.5 sulfuric acidelectrolyte including 0.01M C-8 acid. Results of these half-cellexperiments are illustrated in FIGS. 16 and 17.

[0129]FIG. 16 provides galvanostatic polarization curves for severaldifferent concentrations of TMM for the above-mentioned Pt—Snelectrodes. The Pt—Sn electrodes were of the gas-diffusion type andconsisted of 0.5 mg/cm² of total metal supported on Vulcan XC-72obtained from Etek, Inc., Framingham, Mass. In FIG. 16, current densityin mA/cm² is provided along axis 600 and polarization (in terms ofpotential v. NHE) is provided along axis 602. Curves 604, 606, 608 and610, respectively, illustrate polarization for TMM concentrations Of0.1M, 0.5M, 1M and 2M TMM. FIG. 16 shows that improved polarization isachieved at higher concentration levels. All measurements shown in FIG.16 were obtained at room temperature.

[0130] It is found that TMM can be oxidized at potentials considerablymore negative than methanol. Also, it has been found that temperatureaffects the oxidation rate of TMM. FIG. 17 illustrates polarization attwo different concentrations and at two different temperatures. In FIG.17, current density in mA/cm² is provided along axis 612 andpolarization (in potential Y. NHE) is provided along axis 614. Curve 616illustrates polarization for a 1M TMM concentration at room temperaturewhereas curve 618 illustrates polarization for a 2M concentration of TMMat 55° C. The curves of FIG. 17 were obtained using a Pt—Sn electrode ina 0.5M sulfuric electrolyte including 0.01M C-8 acid. As can be seen,improved polarization is achieved using a higher concentration at ahigher temperature. A comparison of curve 618 of FIG. 17 with curve 610of FIG. 16 illustrates that an increase in temperature yields animproved performance for the same concentration level. Although notshown, it has been found that at temperatures as high as 60° C., therate of oxidation of TMM is twice that at 25° C.

[0131] In addition to the half cell experiments illustrated in FIGS. 16and 17, full fuel cell experiments were also conducted to verify theeffectiveness of TMM in a fuel cell. The direct oxidation of TMM in fuelcells was carried out in a liquid feed type fuel cell of the typeillustrated above in FIGS. 1 and 2. Hence, the fuel cell used the protonconducting solid polymer membrane (Nafion™ 117) as the electrolyte. Themembrane electrode assembly of the fuel cell included unsupportedplatinum-ruthenium catalyst layer (4 mg/cm²)and gas-diffusion typeunsupported platinum electrode (4 mg/cm²) for the reduction of oxygen.The fuel cell used a 2M solution of TMM on the fuel oxidation side andoxygen at 20 psi on the cathode.

[0132] As with DMM, an analysis of the oxidation products of TMM showonly methanol and methanol is considered a possible intermediate in theoxidation of TMM to carbon dioxide and water. For fuel cells which arecompatible with methanol, the presence of methanol as an intermediateproduct is not a concern because the methanol is ultimately oxidized tocarbon dioxide and water.

[0133] The current-voltage characteristics of the above-described liquidfeed direct oxidation fuel cell is shown in FIG. 18 for both TMM andmethanol. Current density in mA/cm² is provided along axis 620 and cellvoltage is provided along axis 622. Curve 624 shows cell voltage as afunction of current density for a 1M concentration of TMM. Curve 626illustrates the same for a 1M concentration of methanol. Themeasurements shown in FIG. 18 were obtained at 65° C. Although notshown, at 90° C., cell voltages can reach 0.52 V at 300 mA/cm² with TMMwhich is higher than that attained with methanol.

[0134] Thus from both half-cell and full-cell measurements it has beenfound that TMN, like DMM, is capable of being oxidized at very highrates. Also like DMM, TMM is a non-toxic, low-vapor pressure liquid,permitting easy handling, and can be synthesized from natural gas(methane) by conventional methods.

[0135] Trioxane as a fuel for a liquid feed fuel cell

[0136] FIGS. 19 -21 illustrate the results of experiments conductedusing trioxane as a fuel for an organic direct liquid feed fuel cell. Aswith DMM and TMM described above, in use, trioxane is mixed with waterto a concentration in the range of about 0.1 to 2M and fed into a fuelcell. Other concentrations may also be effective. The fuel cell may beof conventional design or may include one or more of the improvementsdescribed above. Within the fuel cell, the trioxane is electro-oxidizedat the anode of the cell. The electrochemical oxidation of trioxane isrepresented by the following action:

(CH₂O)₃+6H₂O→3CO₂+12H⁺+12e⁻  (6)

[0137] Experiments verifying the electro-oxidation of trioxane have beenperformed in half-cells similar to the cell shown in FIG. 10 withtemperature control using Pt—Sn electrode with a 0.5M to 2.0M sulfuricacid electrolyte including 0.01M C-8 acid. Results of these half-cellexperiments are illustrated in FIGS. 19 and 20.

[0138]FIG. 19 provides galvanostatic polarization curves for severaldifferent concentrations of trioxane for the above-mentioned Pt—Snelectrodes. The Pt—Sn electrodes were of the gas diffusion type andconsisted of 0.5 mg/cm² of the total noble metal supported on VulcanXC-72 obtained from Etek, Inc., Framingham, Mass. In FIG. 19, currentdensity in mA/cm² is provided along axis 700 and polarization (in termsof potential v. NHE) is provided along axis 702. Curves 704, 706, 708and 710, respectively, illustrate polarization for trioxane atconcentrations of 0.1M, 0.5M, 1M and 2M. FIG. 19 shows that improvedpolarization is achieved at higher concentration levels. Allmeasurements shown in FIG. 19 were obtained at 55° C.

[0139] Hence, for trioxane, increasing fuel concentration results inincreased rate of oxidation. Also, as can be seen from FIG. 19, currentdensities as high as 100 mA/cm² are achieved at potentials of 0.4 V vs.NHE. This performance is comparable to the performances achieved withformaldehyde. Although not shown, cyclic voltammetry studies havedetermined that the mechanism of oxidation of trioxane does not involvea breakdown to formaldehyde before electro-oxidation.

[0140] It has also been found that increasing the acid concentration ofthe electrolyte also results in increased rates of electro-oxidation.FIG. 20 illustrates polarization at four different electrolyteconcentrations and at two different temperatures. In FIG. 20, currentdensity in mA/cm² is provided along axis 712 and polarization (inpotential v. NHE) is provided along axis 714. Curve 716 illustratespolarization for a 0.5M electrolyte concentration at room temperature.Curve 718 illustrates polarization for a 0.5M electrolyte concentrationat 65° C. Finally, curve 722 illustrates polarization for a 2Melectrolyte concentration at 65C. For ° all of curves 716-722, thetrioxane concentration was 2M.

[0141] The curves of FIG. 20 were obtained using a Pt—Sn electrode in asulfuric acid electrolyte including 0.01M C-8 acid. As can be seen,improved polarization is achieved using a higher electrolyteconcentration at a higher temperature. Therefore it was projected thatvery high rates of electro-oxidation are expected with Nafion™ as anelectrolyte since Nafion™ exhibits an acidity equivalent of 10M sulfuricacid.

[0142] In addition to the half cell experiments illustrated in FIGS. 19and 20, full fuel cell experiments were also conducted to verify theeffectiveness of trioxane in a fuel cell. The direct oxidation oftrioxane in fuel cells was carried out in a liquid feed type fuel cellof the type shown above in FIGS. 1 and 2. Hence, the fuel cell used theproton conducting solid polymer membrane (Nafion™ 117) as theelectrolyte. The fuel cell used a 1M solution of trioxane on the fueloxidation side and oxygen at 20 psi on the cathode.

[0143] As with DMM and TMM, an analysis of the oxidation products oftrioxane show only methanol and methanol is considered a possibleintermediate in the oxidation of TMM to carbon dioxide and water. Forfuel cells which are compatible with methanol, the presence methanol asan intermediate product is not a concern because the methanol isultimately oxidized to carbon dioxide and water.

[0144] The current-voltage characteristics of the above-described liquidfeed direct oxidation fuel cell is shown in FIG. 21 for trioxane.Current density in mA/cm² is provided along axis 724 and cell voltage isprovided along axis 726. Curve 728 shows cell voltage as a function ofcurrent density for a 1M concentration of trioxane. The measurementsshown in FIG. 21 were obtained at 60° C. The performance illustrated inFIG. 21 may be improved considerably using platinum-tin electrodes,rather than Pt—Ru electrodes.

[0145] A measurement of crossover, not shown, in the trioxane/oxygenfuel cell suggests that a rate of crossover is at least 5 times lowerthan that in methanol fuel cells. The decreased rates of crossover areextremely desirable since, as described above, crossover affects theefficiency and performance of fuel cells.

[0146] Thus from both half-cell and full-cell measurements it has beenfound that trioxane, like DMM and TMM, is capable of being oxidized atvery high rates.

Conclusion

[0147] What has been described are a variety of improvements to liquidfeed fuel cells including improved electrolyte and electrode structures,improved methods for fabricating electrodes, additives for improvingfuel performance and a set of three new fuels. The various improvementsmay be implemented separately or, for the most part, may be combined toachieve even more enhanced performance. It should be noted, however,that the above-described use of C-8 acid as an additive in a fuel isexpected to be effective only for fuel cells employing an acidelectrolyte such as sulfuric acid and may not be effective if employedusing a fuel cell configured with a proton exchange membrane.

[0148] The methods of embodiments and experimental results shown hereinare merely illustrative and exemplary of the invention and should not beconstrued as limiting the scope of the invention.

What is claimed is:
 1. An aqueous organic fuel-feed fuel cell,comprising: a first electrode having a first polarity; a secondelectrode having a second polarity different than the first polarity; anelectrolyte, comprising a proton-conducting membrane which is coupled toboth said first and second electrodes; and a circulating system,operating to circulate a first liquid organic fuel which issubstantially free of acid-containing electrolytes into an area of saidfirst electrode to cause a potential difference between said first andsecond electrodes when a second component is in an area of said secondelectrode.
 2. A fuel cell as in claim 1, wherein said circulating systemincludes a first pump, pumping the organic fuel, wherein said secondcomponent is oxygen-containing gas.
 3. A fuel cell as in claim 1,wherein said proton-conducting membrane is formed of a solid polymermaterial.
 4. A fuel cell as in claim 3, wherein said membrane includes aco-polymer of tetraflouroethylene and perflourovinylether sulfonic acid.5. A fuel cell as in claim 1, wherein said organic fuel is a combinationconsisting essentially of an aqueous methanol derivative.
 6. A fuel cellas in claim 1, wherein said first electrode is formed of a porousmaterial configured in a way to be wet by the organic fuel.
 7. A fuelcell as in claim 6, wherein said first electrode includes an additivewhich increases wetting properties by decreasing interfacial tension ofan interface between the liquid organic fuel and a catalyst on the firstelectrode.
 8. A fuel cell as in claim 7, wherein said additive is formedof substantially the same material which forms said membrane.
 9. Amethod of operating a fuel cell, comprising: preparing a first electrodeto operate as a first polarity electrode, said first electrode having afirst surface exposed to the fuel; circulating an organic fuel which issubstantially free of any acid electrolyte into contact with said firstsurface of said first electrode, said organic fuel having a componentwhich is capable of electro-oxidation; preparing a second electrodewhich operates as a second polarity electrode, said second polaritybeing different than the first polarity, said second electrode having asecond surface; preparing an electrolyte which includes a protonconducting membrane; circulating a second reactive component intocontact with said second surface of said second electrode, said secondreactive component including a component capable of electro-reduction;and coupling an electrical load between said first electrode and saidsecond electrode, to receive a flow of electrons caused by a potentialdifference between said first and second electrodes.
 10. A method as inclaim 9, wherein said organic fuel includes a methanol derivative andwater and is substantially free of any acid component.
 11. A method asin claim 10, wherein said second reactive component is anoxygen-containing gas.
 12. A method as in claim 11 further comprisingoperating said fuel cell to transport protons from the first electrodethrough the electrolyte to the second electrode, and to form a flow ofelectrons through the load.
 13. An organic fuel cell, comprising: afirst chamber, formed of a plurality of inner surfaces made of amaterial which is not acid resistant, and including a first port,positioned and sized to receive a fuel therein, and a second port sizedto exhaust said fuel therefrom; a first electrode, including anelectrocatalyst operatively coupled thereto, in contact with said firstchamber; an electrolyte, ionically coupled with said first electrode; asecond chamber, having surfaces formed to receive a second componenttherein which is capable of undergoing reduction; a second electrodetonically coupled with said electrolyte and having a second surfaceexposed to said second chamber; and a fuel circulating mechanism,operating to pump said organic fuel into said first chamber and toreceive exhausted fuel therefrom, said fuel circulating mechanism havingsurfaces which contact said fuel which surfaces are not acid resistant.14. A fuel cell as in claim 13, wherein said electrolyte includes aproton-conducting membrane.
 15. A fuel cell as in claim 13, furthercomprising an organic fuel, located in said first chamber, said organicfuel substantially free of any acidic or alkaline component.
 16. A fuelcell as in claim 15, wherein said second component includesoxygen-containing gas.
 17. A fuel cell as in claim 13, wherein saidanode includes an electrocatalyst operatively associated therewith. 18.A fuel cell as in claim 17, wherein said electrocatalyst is a metalalloy particle, said metal alloy including platinum.
 19. A method ofoperating an organic fuel cell, comprising: circulating a mixture of amethanol derivative (RCH₃OH) and water which substantially excludes anyacid components into contact with a first electrode; carrying out anelectrochemical oxidation reaction at the electrode of R—CH₃OH+H₂OCO₂+H⁺+e⁻; simultaneously with the electrochemical oxidation reaction,carrying out a second electrochemical reduction reaction to reduceoxygen and capture electrons at a cathode according to Cathode:O₂+4H⁺+4e⁻H₂O; and attaching a load between said anode and said cathodeto receive electron flow from the reaction.
 20. A method as in claim 19,further comprising coating the anode with an electrocatalyst tofacilitate the reaction.
 21. A method as in claim 19, further comprisingpressurizing air past the cathode at pressures between 10 and 30 psig.22. A fuel cell apparatus, comprising: a first chamber having surfacesfor containing an organic aqueous fuel therein; an anode structure,having a first surface in contact with said first chamber, said anodestructure being porous and capable of wetting the liquid fuel and alsohaving electronic and ionic conductivity; an electrolyte, in contactwith said anode structure, said electrolyte formed of aproton-conducting membrane; a cathode, in contact with said electrolytein a way to receive protons which are produced by said anode structure,conducted through said electrolyte to said cathode; and a secondchamber, holding said cathode, said second chamber including a secondmaterial including a reducible component therein wherein said anode isformed of carbon paper with an electrocatalyst thereon and wherein saidfuel is an aqueous solution of a methanol derivative, and said secondmaterial is an oxygen-containing gas.
 23. A fuel cell as in claim 5,wherein said methanol derivative is dimethoxymethane mixed with water toa concentration of about 0.1 to 2M.
 24. A fuel cell as in claim 5,wherein said methanol derivative includes dimethoxymethane forming anelectro chemical reaction of (CH₃O)₂CH₂+4H₂O CO₂+16H⁺+16e^(−.)
 25. Afuel cell as in claim 5, wherein said methanol derivative istrimethoxymethane mixed with water to a concentration of about 0.1 to2M.
 26. A fuel cell as in claim 5, wherein said methanol derivativeincludes trimethoxymethane, forming an electro chemical reaction of(CH₃O)₃CH+5H₂O 4CO₂+20H⁺+20e⁻.
 27. A fuel cell as in claim 5, whereinsaid methanol substance is trioxane mixed with water to a concentrationof about 0.1 to 2M.
 28. A fuel cell as in claim 5, wherein said methanolderivative includes trioxane, forming an electro chemical reaction of(CH₂O)₃CH₂+6H₂O ₃CO₂+12H⁺+12e⁻.
 29. An aqueous fuel-fed fuel cell,comprising: anode electrode means for producing electrons when the fuelcell is operating; cathode electrode means for receiving electrons whenthe fuel cell is operating; means for circulating a first aqueous andnon-acid organic fuel in an area of one of said electrode means, andcirculating an oxygen-containing gas in an area of the other of saidelectrode means; an electrolyte, comprising a proton conductingmembrane; and connection means, connected respectively to said anodeelectrode means and said cathode electrode means, for producing apotential difference therebetween, allowing a flow of electrons betweensaid anode electrode means and said cathode electrode means, through aload.
 30. An organic fuel cell, comprising: a first chamber, formed of aplurality of inner surfaces made of a first material; a first electrode,including an electrocatalyst thereon, said first electrode being incontact with said first chamber, an electrolyte, ionically coupled withsaid anode electrode; a second electrode tonically coupled with saidelectrolyte; and a mechanism operating to pump said fuel into said firstchamber and to receive exhausted fuel therefrom, said mechanism havingsurfaces which contact said fuel; wherein at least one of the surfaceswhich contacts said organic fuel is formed of a material which is notacid resistant.
 31. A method of oxidizing aqueous methanol in a fuelcell reaction, comprising: receiving aqueous methanol at an anode;oxidizing said aqueous methanol at the anode; producing protons from theaqueous methanol oxidizing at the anode; allowing the protons to cross aproton conducting membrane to a cathode and reducing a second component,at the cathode, using said protons which are produced at said anodewherein said aqueous methanol is substantially free of an acidcomponent, said protons being produced from said oxidizing reaction. 32.A method of operating a fuel cell, comprising: preparing a firstelectrode to operate as a first polarity electrode, said first electrodehaving a first surface exposed to the fuel; modifying said firstelectrode in a way to bring the fuel into better contact with the firstelectrode by its wetting of the first electrode; circulating an organicfuel which is substantially free of any acid electrolyte into contactwith said first surface of said first electrode, said organic fuelhaving a component which is capable of electro-oxidation; preparing asecond electrode which operates as a second polarity electrode, saidsecond polarity being different than the first polarity, said secondelectrode having a second surface; preparing an electrolyte whichincludes a proton conducting membrane; circulating a second reactivecomponent into contact with said second surface of said secondelectrode, said second reactive component including a component capableof electro-reduction to form a reaction.
 33. Method as in claim 32wherein said wetting comprises treating the anode electrode with aproton conducting agent.
 34. A method of operating an organic fuel cell,comprising: circulating a mixture of a methanol derivative (R—CH₃OH) andwater contact with a first electrode; carrying out an electrochemicaloxidation reaction at the first electrode of R—CH₃OH+H₂O CO₂+H⁺+e⁻ tothereby create protons from the electro-chemical oxidation reaction;allowing said protons created at the first electrode to pass through aproton conducting membrane to a second electrode; substantiallysimultaneously with the electro-chemical oxidation reaction, carryingout a second electrochemical reduction reaction to reduce oxygen andcapture electrons at the second electrode, using the protons created atthe first electrode, according to Cathode: O₂+4H⁺+4e⁻ H₂O; to therebyform a potential difference between said first and second electrodes.